At the Transformational Climate Science conference in my home town, Exeter, UK, earlier this month, senior IPCC author Ottmar Edenhofer discussed the ‘battle’ with governments on his part of the report. Another scientist who worked on the report highlighted confidentially to me how unusual the omission was.

To me, it’s more surprising that this hasn’t happened more often, especially when you look more closely at the latest report’s findings. There’s concrete certainty that warming is happening, and it’s extremely likely that humans are the dominant cause, it says. Governments have even – in some cases, begrudgingly – already signed up to temperature and CO2 emission targets reflecting this fact.

The inadequacy of those words is becoming ever more starkly obvious. Ottmar stressed that the emissions levels agreed at the United Nations’ Climate Change Conference in Cancún, Mexico, in November 2010, would likely need later emissions cuts the likes of which we’ve never seen before to avoid dangerous climate change. The latest IPCC report shines a floodlight on that inertia, which understandably cranks up the tension between researchers and politicians.

Ottmar was one of two co-chairs who led the ‘working group three’ (WGIII) section of the IPCC report that looks at how to cut greenhouse gas emissions. He stressed that the need to make these cuts comes from a fundamental difference between the risks that come from climate change and the risks of mitigation. We can heal economic damage arising from cutting emissions – reversing sea level rise isn’t so easy.

Jim Hansen giving testimony at a US Congressional hearing in 1988, where he’d declare 99% certainty that humans are changing the climate. Image credit: NASA

“It’s time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here.” It’s a comment that wouldn’t sound out of place today, but Jim Hansen made it 26 years ago, on June 23, 1988, amid record 38°C temperatures in Washington DC. Jim said it to reporters after telling a Congressional hearing he was 99% certain the world is getting warmer thanks to human-made greenhouse gases.

Jim’s 1980s media bombshells led journalist Robert Pool to liken him to a religious ‘witness’, ‘someone who believes he has information so important that he cannot keep silent’. However, he still felt shy and awkward, preferring to immerse himself in pure science, and so would turn down almost all invitations to speak out for another decade. Jim’s efforts during that period would then help build even stronger evidence on global warming. But with extra motivation provided by clashes with the US government and the arrival of his grandchildren he would return to bear witness more forcefully than ever.

Before his self-imposed media ban Jim would make headlines one more time in 1989, after giving written evidence to a hearing convened by then US senator Al Gore. The testimony reaching the hearing had been altered by the White House to make his conclusions about the dangers of global warming seem less certain. When Jim sent the future vice-president a note telling him this, he alerted the media, turning their scheming into the lead story across all TV networks that evening. John Sununu, aide to then president George H. W. Bush, would then try to get Jim fired for his troubles. But Republican senator John Heinz intervened on Jim’s behalf, and he kept his job.

Wheat ear infected with Fusarium ear blight (FEB), giving the ear a pinkish color. The disease could be set to increase in countries like China and the UK with climate change, Bruce Fitt and his teammates have found, suggesting resistant varieties should be developed. Photo credit: CIMMYT.

As the planet warms, China’s wheat crops will be threatened by more frequent epidemics of ‘fusarium ear blight’ (FEB), scientists in the UK and China have projected. Bruce Fitt from the University of Hertfordshire in Hatfield, UK, and his teammates forecast levels of the disease in the Anhui and Hubei provinces from 2021-2050. Whereas in the worst affected regions in 2001-2010 around one-sixth of all ears were infected, this was the lowest disease level the researchers found in their future scenario. In the worst-hit areas, FEB infected more than a third of all ears. “This has implications for crop breeding because it takes 10-15 years to breed a new cultivar,” Bruce told me. “If you know the disease is going to become more important then you need to get on and start breeding now rather than waiting until the disease hits you.”

Today, over a billion people don’t have enough to eat, and further population growth and climate change are set to put the world’s food supplies under even greater strain. To help ease that pressure, Bruce and other scientists are working to understand and help improve control of crop diseases like FEB. While some crop diseases will worsen in the future, not all will, he stressed. “For example, you might have a disease that is spread by rainsplash in summer and then it’s predicted that there will be far less rainfall in summer,” he explained. “Then you would expect that with climate change the importance of that disease would diminish.” If governments, farmers and seed suppliers know which diseases are likely to get worse, they can prioritise developing strategies to contol them, like breeding disease resistant varieties.

To make useful forecasts for which diseases will worsen, scientists build models that include weather data, how crops grow and how the disease pathogen spreads through the crop. “In this particular instance the wheat is susceptible only at flowering,” Bruce said. “It may be in flower for a few days. If it doesn’t get the pathogen inoculum and the right weather conditions at that time it will not get the disease.” Climate change can both alter flowering times and the chances of warm, wet weather that make infection more likely. When wheat gets infected, even if it can be harvested it is more likely to contain poisonous mycotoxins. “If it’s full of mycotoxins then it can’t be eaten by man or beast, so it’s just wasted,” Bruce added. Read the rest of this entry »

The sources of data that scientists can use to determine climate sensitivity include ice cores, the cylinders these researchers are holding at the Vostok station in Antarctica. Image credit: Todd Sowers, Columbia University

How much does the world warm up in response to a certain amount of greenhouse gases like CO2 in the atmosphere? It’s a simple question, but its answer depends on whether you mean short-term or long-term warming, and estimates vary according to the methods used. Scientists are currently intensively debating long-term ‘climate sensitivity’, which begs prompts the question: might we be pushing too hard to cut climate CO2 emissions, if this is uncertain?

The answer is no, according to Joeri Rogelj from the Swiss Federal Institute of Technology, ETH Zurich, and his coworkers. They looked at how a range of climate sensitivity values affected their 21st century warming projections in a paper published in Environmental Research Letters last week. “When taking into account all available evidence, the big picture doesn’t change,” Joeri told me. The ‘carbon budget’ of greenhouse gases we could still emit today and in the future is very limited whatever the climate sensitivity, he explained. “Keeping the so-called carbon budget in line with warming below 2°C still requires a decarbonisation of global society over the first half of this century.”

Climate sensitivity is the measure of how much the world will eventually warm when it reaches equilibrium after a doubling of CO2 in the air. Today, we have upset the normal equilibrium where the Sun’s energy flowing into the atmosphere matches the flow the Earth radiates back out of it. Now more is coming in than leaving, and that’s heating the planet up. Think of the atmosphere as a series of pipes, with energy flowing through them like a liquid. The Earth is a reservoir in the system, filled by an incoming pipe and drained by an outgoing one. CO2 acts like a blockage in the outgoing pipe – it slows the outward energy flow and causes a build-up in the reservoir. When the reservoir gets fuller it can put enough pressure on the blockage for the outward flow through it to again match the incoming flow. Then we’d be at equilibrium, but with a fuller reservoir – a warmer planet. The more CO2 we emit, the worse the blockage gets and the hotter we get before reaching equilibrium. Read the rest of this entry »

The world’s surface air temperature change (“anomaly”), relative to the world’s mean temperature of 58° F or 14.5° C, averaged over land and oceans from 1975 to 2008. Inset are two periods of no warming or cooling within this overall warming trend. Copyright 2009 American Geophysical Union. Reproduced/modified by permission of Wiley/American Geophysical Union, see citation below.

Starting climate models from measured data helps simulate the early-2000s global warming hiatus better, and reduces projections for warming through to 2035. Jerry Meehl and Haiyan Teng have compared such ‘initialised’ model runs against more common ‘uninitialised’ ones starting without real-life conditions. The scientists, from the US National Centre for Atmospheric Research (NCAR) in Boulder, Colorado, find initialised runs get closer to modelling that hiatus and surprisingly rapid warming in the 1970s. Using the same approach, admittedly rough 30-year predictions for Earth’s surface air temperature initialised in 2006 are about one-sixth less than uninitialised projections. “We have evidence that if we would have had this methodology in the 1990s, we could have predicted the early-2000s hiatus,” Jerry told me.

The hiatus Jerry and Haiyan studied – an easing off in the rate of global warming since 1998 – is perhaps the aspect of climate change most hotly debated today. But hiatus is a slippery word, whose meaning depends on who is highlighting what points on which graph. Climate skeptics will often infer that it’s evidence that global warming is not a problem, or that it shows we know too little to act on climate change. The UN Intergovernmental Panel on Climate Change puts it in plain numbers: the rate of warming from 1998-2012 was 0.05°C per decade; from 1951 to 2012, it was 0.12°C per decade. “In addition to robust multi-decadal warming, global mean surface temperature exhibits substantial decadal and interannual variability,” it adds. “Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends.”

Steve Schneider juggled with the dilemma of conveying the urgency of climate change, while conveying how we can be confident about that when the evidence is sometimes uncertain Credit: L.A. Cicero, Stanford University News.

This is part three of this profile. You can also read part one and two.

“Each of us has to decide what the right balance is between being effective and being honest.” Those are words – seemingly advising his colleagues to lie to shape public opinion – credited to climate scientist Stephen Schneider in a 1989 Discover magazine article. Because of that quote, Steve was told, a number of US congressional hearings chose not to invite him as an expert witness.

With extreme irony, it came from an interview where Steve was expressing frustration after having been misrepresented in the media. He later argued that he was trying to explain how to succeed faced with the “double ethical bind” of being effective and honest in conveying both uncertainty and urgency. Even in the original article he adds, “I hope that means being both” – something often overlooked in scandalised reactions to his words. But perhaps the trouble this caused Steve in fact reflects the strangeness of the idea he dedicated much of his career to getting across. How can scientific projections with an element of uncertainty lead to the conclusion that we must act on climate change urgently?

We’re instinctively uncomfortable with uncertainty, and so Steve wanted clearer ways to get it across in the UN Intergovernmental Panel on Climate Change (IPCC)’s second climate change assessment report. At a meeting in 1994 he pushed for their estimates to come as probability distributions showing the odds for each in a range of different values. This could be done, he argued, for everything from damage likely to be caused by global warming to values for numbers central to natural processes, like climate sensitivity.

With no-one backing Steve, ambiguity crept into the report. Did everyone think that saying they had “high confidence” in a statement meant the same thing? After the second report, returning to his recently-appointed post at Stanford University in California, he was determined to hammer out any doubt. Together with the IPCC’s Richard Moss, Steve found 100 examples of inconsistent use of such terms. Armed with that shocking finding they persuaded the IPCC’s working group I, which discusses the physics of climate change, to define clear scales.

The result would be a double strategy, with verbal scales both for the probability of a forecast and for the reliability of the underlying science. For probabilities, low confidence meant a less than 1-in-3 chance, medium between 1-in-3 and 2-in-3 and high 2-in-3 and above. Very high confidence meant a 19-in-20 chance, and very low confidence 1-in-20. There were four grades for the quality of science, ranging from ‘speculative’ to ‘well established’. Reading through thousands of draft pages ensuring consistency in the run-up to the IPCC’s third report, published in 2001, Richard and Steve became known as the ‘uncertainty police’. Read the rest of this entry »

“How many of you think the world is cooling?” That’s what Steve Schneider asked the studio audience of the Tonight Show with Johnny Carson in September 1977. And when the majority put their hands up, he explained that the recent cooling trend had only been short-term. Though the unscripted poll meant Steve wasn’t invited back to the programme, through the summer of that year he had brought climate science to US national TV. The appearances typified Steve’s efforts to bring climate change to the world’s notice – efforts that would later draw attention of a less desirable sort.

Building on his earlier high profile research, Steve had just published ‘The Genesis Strategy: Climate and Global Survival’, predicting ‘demonstrable climate change’ by the end of the century. Whether human pollution would cause warming or cooling, he argued governments should copy the biblical story where Joseph told Pharoah to prepare for lean years ahead. In a decade already torn by rocketing food and oil prices, the advice resonated with many who wanted to head off any further crises.

Some scientists criticised Steve and those like him for speaking straight to the public. In particular, climate science uncertainties were so great that they feared confusion – like that over whether temperatures were rising or falling – was inevitable. That dispute grew from a basic question about science’s place in society. Should researchers concentrate on questions they can comfortably answer using their existing methods? Or should they tackle questions the world needs answered, even if the results that follow are less definite?

At a meeting to discuss climate and modelling research within the Global Atmospheric Research Programme (GARP) in 1974 near Stockholm, Sweden, Steve pushed for the second approach. Given the food problems the world was struggling with at the time, it seemed obvious that climate change impacts like droughts, floods and extreme temperatures would bring famines. “I stood alone in arguing that we had to consider the implications of what we were researching,” Steve later wrote. While some attacked him angrily, saying they weren’t ready to address these problems, conference organiser Bert Bolin agreed that socially important questions must be answered.

The suggestion was also controversial because it meant blurring the lines between climate science and other subjects, such as agriculture, ecology and even economics. The director at the US National Center for Atmospheric Research (NCAR) in Boulder, Colorado, where Steve worked, warned that crossing subject boundaries might cost him promotion. But he responded with characteristic wilfulness, founding a journal doing exactly what he was warned not to. Read the rest of this entry »